'Every metre is mined'

"It's been a long time since we came to al-Bab but today we can say that near complete control has been taken of al-Bab and the city centre has been entered," Mr Isik was quoted as saying by Anadolu news agency.

"When the search and combing operations are over, we will be able to say that al-Bab has been completely cleared of Daesh [IS] elements. This does not need too much more time," he said.

An FSA fighter in al-Bab told Reuters news agency by telephone that the city centre had been reached on Wednesday but a suicide attack had forced the FSA fighters back.

Following a new push on Thursday, 85-90% of the town was under FSA control, he said.

"The whole of the city is mined," he said. "I can say that every metre is mined."

The IS news agency, Amaq, said there had been fierce fighting in al-Bab on Wednesday.

It referred to the battle for the town in the past tense, apparently acknowledging that it was over.

Situated just north-east of Aleppo, al-Bab has about 100,000 inhabitants in the centre and about 50,000 more living in the suburbs.

It fell to Syrian rebels in spring 2012 and was in IS hands by early 2014, when it became home to many foreign jihadists and their families.

Turkish President Recep Tayyip Erdogan said last year that the capture of al-Bab, the jihadist group's last major stronghold in Aleppo province, would be the prelude to taking Raqqa, seen by IS as its capital in Syria.